Dice or shred corned beef. Combine corned beef with sauerkraut and set aside.
Melt butter in large soup pot over low heat. Add flour and heat 3-5 minutes, stirring constantly to cook flour and make a roux.
Stir in cream and milk. Add onions. Increase heat to medium and continue cooking 7-10 minutes, stirring constantly, until soup thickens. Add cheese and stir to blend. Add white pepper, garlic salt, onion powder, celery salt, lemon pepper and salt. Add corned beef and sauerkraut.
Stir until well-combined. Makes about 2 quarts, serving 4-6 people.